A Si heterojunction field effect transistor (HJFET) was developed as a high-performance and low-cost alternative to the conventional thin-film transistor (TFT) on single or poly-crystalline Si substrates. Compared to a conventional TFT, in an HJFET: (i) gate dielectric is replaced with a stack of doped crystalline and/or non-crystalline semiconductor materials such as hydrogenated amorphous silicon (a-Si:H) grown by a deposition process such as plasma-enhanced chemical vapor deposition (PECVD), (ii) source/drain contacts are replaced with doped crystalline and/or non-crystalline semiconductor materials such as hydrogenated crystalline silicon (c-Si:H) and (iii) lightly-doped drain (LDD) regions are omitted. The HJFET enables significant cost reduction by employing the PECVD of a-Si:H and c-Si:H instead of the expensive process steps used for the conventional TFT and is particularly appealing for producing large-sized displays on low-temperature poly-Si (LTPS) substrates.